Method for forming a metal line and method for manufacturing display substrate having the metal line

ABSTRACT

A method for forming a metal line includes sequentially depositing a low-resistivity metal layer having aluminum on a base substrate and an upper layer having molybdenum on the low-resistivity metal layer, forming a photoresist pattern having a linear shape on the upper layer, etching the upper layer via a mixed gas using the photoresist pattern as a mask, the mixed gas including a chlorine based gas mixed with an additional gas having at least one of nitrogen gas, argon gas, helium gas and sulfur hexafluoride gas, and etching the low-resistivity metal layer using the photoresist pattern as the mask thereby removing any stringer that may be caused by a residue of the low-resistivity metal layer.

REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to Korean PatentApplication No. 2006-99184, filed on Oct. 12, 2006, in the KoreanIntellectual Property Office (KIPO), the contents of which in itsentirety are herein incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a displaysubstrate and, more particularly, to a method of manufacturing a displaysubstrate having a metal line exhibiting reduced resistance.

2. Description of the Related Art

Generally, a liquid crystal display (“LCD”) apparatus includes a displaysubstrate, a counter substrate, and a liquid crystal layer disposedbetween the display substrate and the counter substrate. Gate lines andsource lines whose longitudinal directions cross each other are formedon the display substrate. A switching element, electrically connected tothe gate and source lines and a pixel electrode, electrically connectedto the switching element, are formed on the display substrate.

As display apparatus have become larger the RC delay of the metal layerformed on the display substrate has increased. To minimize the RC delay,the metal layer is formed by using aluminum having a low resistance.However, many defects may be generated in manufacturing an aluminummetal layer which also tends to exhibit a high contact resistance withother layers.

Thus, a double layer structure or a triple layer structure having a lowresistivity metal layer is employed that may include an aluminum (Al)layer and a molybdenum (Mo) layer while the triple layer structure mayinclude a first molybdenum (Mo) layer, an aluminum (Al) layer and asecond molybdenum (Mo) layer.

In order to form the low resistivity metal layer structure, themolybdenum layer is etched by using a chlorine based gas mixed withoxygen gas. Because the chlorine based gas mixed with oxygen has highreactivity, contamination may be a problem. In addition, the mixed gasreacts with aluminum forming an undesired aluminum oxide layer allowinga stringer of the aluminum layer to remain at the edge of a pattern.

SUMMARY OF THE INVENTION

According to an aspect of the present invention a display substratehaving an accurately formed metal layer of low resistance is made bydepositing, on a base substrate, a low resistivity aluminum layer andthen sequentially depositing an upper layer having molybdenum on the lowresistivity metal layer. A photoresist pattern having a linear shape isformed on the upper layer. The upper layer is etched using a mixed gaswith the photoresist pattern as a mask. The low resistivity metal layeris etched using the photoresist pattern as the mask. The mixed gasincludes a chlorine based gas mixed with an additional gas having atleast one of nitrogen gas, argon gas, helium gas and sulfur hexafluoridegas.

In an exemplary method for manufacturing the display substrate accordingto the present invention, a gate insulating layer is formed on a basesubstrate, and a gate pattern having a gate line and a gate electrode isformed on the base substrate. A source metal layer is formed bysequentially forming a lower layer, a low-resistivity layer, and anupper layer on the gate insulating layer. A source pattern having asource line, a source electrode and a drain electrode, is formed byetching the upper layer using a mixed gas including a chlorine based gasmixed with an additional gas having at least one of nitrogen gas, argongas, helium gas and sulfur hexafluoride gas. A protective insulatinglayer having a contact hole is formed in the protective insulatinglayer. A pixel electrode electrically connected to the drain electrodethrough the contact hole is formed. The lower layer has molybdenumformed on the gate insulating layer. The low-resistivity metal layer hasaluminum formed on the lower layer. The upper layer has molybdenumformed on the low-resistivity metal layer. The contact hole partiallyexposes the drain electrode.

According to the present invention, etching of the molybdenum layerformed on the aluminum layer is performed so that a stringer that thealuminum layer includes may be removed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detailed example embodimentsthereof with reference to the accompanying drawings, in which:

FIGS. 1A to 1D are sectional views illustrating a method for forming ametal layer according to a first example embodiment of the presentinvention;

FIG. 2 is a schematic view illustrating a reactive ion etcher inaccordance with one embodiment of the present invention;

FIG. 3 is scanning electron microscope images illustrating etchingstringers according to a power density in etching conditions for uppermolybdenum;

FIG. 4 is a plan view illustrating a display substrate according to anexample embodiment of the present invention;

FIGS. 5A to 8 are cross-sectional views illustrating a method formanufacturing a display substrate according to a second exampleembodiment of the present invention; and

FIGS. 9 to 12 are cross-sectional views illustrating a method formanufacturing a display substrate according to a third exampleembodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which embodiments of the invention are shown.In the drawings, the size and relative sizes of layers and regions maybe exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures.

Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected.

Example Embodiment 1 Method for Forming a Metal Line

FIGS. 1A to 1D are sectional views illustrating a method for forming ametal layer according to a first example embodiment of the presentinvention. FIG. 2 is a schematic view illustrating a reactive ion etcher(“RIE”) in accordance with one embodiment of the present invention.

Referring to FIG. 1A, an insulating layer 110 is formed on a basesubstrate 101. A metal line layer 120 is formed on the insulating layer110.

The metal line layer 120 includes a triple layer having a lower layer121, a low resistivity metal layer 122, and an upper layer. The lowerlayer 121 includes molybdenum or molybdenum alloy. The low resistivitymetal layer 122 includes aluminum or aluminum alloy. The upper layer 123includes molybdenum or molybdenum alloy.

A photoresist pattern 140 is formed to correspond to a metal line, viacoating and patterning a photoresist layer on the metal line layer 120.The metal line layer 120 is dry-etched by using the photoresist pattern140.

A dry-etching process, a post-treatment process and an ashing processwhich will be explained, are performed by using the RIE illustrated inFIG. 2.

Referring to FIG. 2, the RIE 200 includes a vacuum chamber 210, an RFgenerator 212 and a power supply part 214, so that etches a substrate100 by using an etching gas. The vacuum chamber 210 includes a lowerelectrode 220, a ground cover part 230, an upper electrode 240, a gassupply part 250, and a vacuum pump part 260.

The lower electrode 220 is disposed over the ground cover part 230, andis connected to the RF generator 212 to receive an RF power. Thesubstrate 100 is disposed on the lower electrode 220. The upperelectrode 240 is disposed over the lower electrode 220, and iselectrically connected to the vacuum chamber 210 directly. In this case,the upper electrode 240 may be replaced with the vacuum chamber 210. Inthis case, the lower electrode 220 is used as a cathode, and the upperelectrode 230 is used as an anode.

The gas supply part 250 provides a gas that will be used for thedry-etching, ashing and post-treatment processes into the vacuum chamber210. The gas provided by the gas supply part 250 is discharged by the RFpower, so that plasma is formed.

The vacuum pump part 260 emits the gas inside of the vacuum chamber 210into an exterior, so that maintains the vacuum chamber 210 in a vacuumstate.

Then, referring to FIGS. 1A and 2, the dry-etching, ashing andpost-treatment processes on the substrate 100 having the metal linelayer 120 formed on the substrate 100 will be explained.

Referring to FIGS. 1A and 2, the substrate 100 that has the photoresistpattern 140 formed on the substrate 100, is disposed on the lowerelectrode 220 in the vacuum chamber 210.

The vacuum chamber 210 is set to a first dry-etching condition, andthen, an oxygen layer (not shown) formed on the upper layer 121 isremoved. The first dry-etching condition is that a pressure is about 15mT, a source power is about 2000 W, and the etching gas of 100BCl₃ isused. The source power and the bias power that will be explained beloware powers applied to the lower electrode 220.

Referring to FIGS. 1B and 2, after removing the oxygen layer formed onthe upper layer 123, the vacuum chamber 210 is set to a seconddry-etching condition, and then the upper layer 123 is etched.

The second dry-etching condition is that the pressure is about 15 mT,the source power density which is defined as the source power divided byan area of the electrode is between about 1 W/cm² and about 2 W/cm², andthe bias power density which is defined as the bias power divided by thearea of the electrode is between about 0.3 W/cm² and about 0.6 W/cm².The area of the electrode is defined as the area of the lower electrode220. The etching gas is a mixed gas including a chlorine based gas (forexample, C₁₂ or HCl) mixed with an additional gas having one of nitrogengas (N₂), argon gas (Ar), helium gas (He) and sulfur hexafluoride gas(SF₆). A ratio of the additional gas with respect to the chlorine basedgas is between about 50% and about 200%. The upper layer 123 is etchedwith the second dry-etching condition, to form the upper pattern 123 a.

Referring to FIGS. 1C and 2, after etching the upper layer 123, thevacuum chamber 210 is set to a third dry-etching condition, and then theoxygen layer formed on the low-resistivity metal layer 122 is removed.

The third dry-etching condition is that the pressure is about 15 mT, thesource power is about 2000 W, and the etching gas of 20C₁₂/100BCl₃ thatis the chlorine based gas mixed with BCl₃ is used. The oxygen layerformed on the low-resistivity metal layer 122 is removed with the thirddry-etching condition.

After the oxygen layer formed on the low-resistivity metal layer 122 isremoved, the vacuum chamber 210 is set to a fourth dry-etchingcondition, and then the low-resistivity metal layer 122 is etched.

The fourth dry-etching condition is that the pressure is between about10 mT and about 30 mT, the source power density is between about 0.7 andabout 1.8, and the bias power density is between about 0.7 and about1.8. The mixed gas that is the chlorine based gas mixed with one of BCl₃gas, nitrogen gas (N₂) and argon gas (Ar) is used as the etching gas.Preferably, the mixed gas that is the chlorine based gas (for example,C₁₂ or HCl) mixed with one of nitrogen gas (N₂) and argon gas (Ar) isused. A ratio of nitrogen gas (N₂) or argon gas (Ar) with respect to thechlorine based gas is between about 50% and about 150%.

The low-resistivity metal layer 122 is etched with the fourthdry-etching condition, to form a low-resistivity pattern 122 a.

Referring to FIGS. 1D and 2, after etching the low-resistivity metallayer 122, the vacuum chamber 210 is set to a fifth dry-etchingcondition, and then, the lower layer 121 is etched. The fifthdry-etching condition is that the power is between about 15 mT and about100 mT, the source power is about 1000 W. The mixed gas that is thechlorine based gas mixed with the additional gas having one of nitrogengas (N₂), argon gas (Ar), helium gas (He) and sulfur hexafluoride gas(SF₆) is used as the etching gas. The ratio of the additional gas withrespect to the chlorine based gas is about 200%. The lower layer 121 isetched to form a lower pattern 121 a.

According to the dry-etching process, a metal line 120 a having the lowresistance is formed on the base substrate 101.

When forming the metal line, a chlorine ion remains on the basesubstrate 101 due to chlorine gas C₁₂ that the etching gas includes.When the chlorine ion remaining on the base substrate 101 is exposed tothe atmosphere, the chlorine ion is reacted with moisture in theatmosphere to form hydrochloric acid (HCl). HCl corrodes thelow-resistivity pattern 122 a including aluminum (Al), so that linestringers occur.

Thus, after forming the metal line, the post-treatment process isperformed to remove the chlorine ion remaining on the base substrate101. To perform the post-treatment process, at least one of H₂ gas andH₂0 gas is provided into the vacuum chamber 210.

H₂ gas or H₂0 gas provided into the vacuum chamber 210 is dissociated bya plasma discharge to generate a hydrogen ion (H+). The hydrogen ion(H+) is reacted with the chlorine ion remaining on the base substrate101, to generate hydrochloric acid (HCl). HCl generated from the vacuumchamber 210 is generated and evaporated at the same time due to anequilibrium vapor pressure. The evaporated HCl is emitted outside of thevacuum chamber 210 through the vacuum pump part 260. Accordingly, thechlorine ion remaining on the base substrate 101 is removed, so that thecorrosion of the low-resistivity pattern 122 a may be prevented.

Alternatively, the post-treatment process may be performed by using afluorine (F) based gas in spite of H₂ gas or H₂0 gas.

For example, the fluorine based gas provided into the vacuum chamber 210is discharged by the RF power, so that the plasma is formed. Thus,fluorine radical is generated. The fluorine radical has a betterreactivity than the chlorine ion. Thus, the fluorine radical is reactedwith the low-resistivity pattern 122 a on an exposed surface of thelow-resistivity pattern 122 a, to substitute the remaining chlorine ion.Accordingly, a corrosion preventing layer including aluminum fluoride(AlF) is formed on the exposed surface of the low-resistivity pattern122 a. Thus, the corrosion of the low-resistivity pattern 122 a may beprevented.

Before the post-treatment process or after the post-treatment process,oxygen gas is provided into the vacuum chamber 210, to perform theashing process that removes the photoresist.

Referring to Tables 1, 2, 3 and FIG. 3, effects of etching themolybdenum layer with the etching conditions of the present exampleembodiment will be explained.

Tables 1, 2, and 3 show etching uniformity of the molybdenum layer withthe etching conditions of the present example embodiment. The etchinguniformity means uniformity in etching quantity of the molybdenum layer.For example, the etching uniformity is a value of measuring surfacetopography after the etching process, to find out how uniformly themolybdenum layer is etched in the base substrate. Thus, the surfacetopography having a lower value may be better in the uniformity.

Tables 1, 2 and 3 show results after etching the single molybdenum layerusing a test substrate having the single molybdenum formed on the testsubstrate, when a nitrated silicon layer (g-SiNx), an amorphous siliconlayer (a-Si) and an n⁺ ion doped layer are sequentially formed.

Tables 1 and 2 show results after etching an upper molybdenum layer inthe single molybdenum layer including Mo/Al/Mo layer. Table 3 showsresults after etching a lower molybdenum layer in the single molybdenumlayer including Mo/Al/Mo layer.

Referring to Tables 1, 2 and 3, the oxygen layer was removed beforeetching the single molybdenum layer. The etching condition for removingthe oxygen layer was that the pressure was about 15 mT, the source powerwas about 2000 W, and the etching gas of 100BCl₃ was used.

TABLE 1 Stacked layer Glass/g-SiNx/a-Si/n⁺ a-Si/Mo Mo-t oxygen layeretching condition Pressure(15 mT), Source power(2000 W), Gas(100BCl₃),Size(20″) Mo-t main etching condition Comparative Example 1 Example 1Example 2 Example 3 (#1) (T#1) (T#2) (T#3) 15 mT, 15 mT, 15 mT, 15 mT,1500 W, 1500 W, 1500 W, 1500 W, 25Cl₂/50O₂ 25Cl₂/50N₂ 25Cl₂/50Ar₂25Cl₂/50He Etching rate 3285 1450 1356 1537 [Å/min] Etching 3.7 5.2 3.77.9 uniformity [%]Table 1 shows results after etching the upper molybdenum layer (Mo-t)with a main etching condition that the pressure was about 15 mT, thesource power was about 1500 W, and the ratio of the additional gas withrespect to the chlorine based gas was about 2:1.

In Comparative Example 1 (#1), the conventional etching gas, for examplethe chlorine based gas mixed with oxygen gas (O₂), was used. In thatcase, an etching rate (E/R) was about 3285 Å/min and the etchinguniformity was about 3.7%.

In Example 1 (T#1), the etching gas including the chlorine based gasmixed with oxygen gas (O₂), was used. In that case, the etching rate(E/R) was about 1450 Å/min and the etching uniformity was about 5.2%. InExample 2 (T#2), the etching gas including the chlorine based gas mixedwith argon gas (Ar), was used. In that case, the etching rate (E/R) wasabout 1356 Å/min and the etching uniformity was about 3.7%.

In Example 3 (T#3), the etching gas including the chlorine based gasmixed with helium gas (He), was used. In that case, the etching rate(E/R) was about 1537 Å/min and the etching uniformity was about 7.9%.

When Comparative Example 1 is compared with Examples 1, 2 and 3, theetching rate (E/R) in Examples 1, 2 and 3 is smaller than that of inComparative Example 1, but Examples 1, 2 and 3 may be enough to beapplied to the etching process. The etching uniformity in Example 2 issubstantially the same as that in Comparative Example 1, and the etchinguniformity in Examples 1 and 3 is substantially same as that inComparative Example 1.

TABLE 2 Stacked layer Glass/g-SiNx/a-Si/n⁺ a-Si/Mo Mo-t oxygen layeretching condition Pressure(15 mT), Source power(2000 W), Gas(100BCl₃),Size(20″) Mo-t main etching condition Example 4 Example 5 Example 6(T#4) (T#5) (T#6) 15 mT, 15 mT, 15 mT, 2000 W, 2000 W, 2000 W,60Cl₂/60N₂ 60Cl₂/60Ar₂ 60Cl₂/60He Etching rate [Å/min] 2338 2406 2431Etching uniformity [%] 8.9 7.5 8.2Table 2 shows results after etching the upper molybdenum layer (Mo-t)with the main etching condition that the pressure was about 15 mT, thesource power was about 2000 W, and the ratio of the additional gas withrespect to the chlorine based gas was about 1:1. In Table 2, the ratioof the chlorine based gas in the etching gas was controlled to be higherthan in Table 1.

In Example 4 (T#4), the etching rate (E/R) was about 2338 Å/min and theetching uniformity was about 8.9%. In Example 5 (T#5), the etching rate(E/R) was about 2406 Å/min and the etching uniformity was about 7.5%. InExample 6 (T#6), the etching rate (E/R) was about 2431 Å/min and theetching uniformity was about 8.2%.

When Examples 1, 2 and 3 in Table 1 is compared with Examples 4, 5 and 6in Table 2, the value of the etching uniformity in Examples 4, 5 and 6is increased so that the etching uniformity is a little worse than inExamples 1, 2 and 3. However, the etching rate (E/R) is somewhatincreased in Examples 4, 5 and 6.

Accordingly, when Examples 1, 2 and 3 in Table 1 are compared withExamples 4, 5 and 6 in Table 2, the etching rate (E/R) is substantiallysame, and the etching uniformity is enough.

TABLE 3 Stacked layer Glass/g-SiNx/a-Si/n⁺ a-Si/Mo Mo-b oxygen layeretching condition Pressure(15 mT), Source power(2000 W), Gas(100BCl₃),Size(20″) Mo-b main etching condition Comparative Example 2 Example 7Example 8 Example 9 (#2) (T#7) (T#8) (T#9) 100 mT, 1000 W, 100 mT, 1000W, 100 mT, 1000 W, 100 mT, 1000 W, 50Cl₂/200O₂ 50Cl₂/200N₂ 50Cl₂/200Ar₂50Cl₂/200He Etching rate 3508 1437 1684 1637 [Å/min] Etching uniformity6.8 6.7 6.9 7.1 [%]Table 3 shows results after etching the lower molybdenum layer (Mo-b)with the main etching condition that the pressure was about 100 mT, thesource power was about 1000 W, and the ratio of the additional gas withrespect to the chlorine based gas was about 4:1.

In the main etching condition of the lower molybdenum layer (Mo-b), aselective ratio should be higher than in the main etching condition ofthe upper molybdenum layer (Mo-t) illustrated in Tables 1 and 2, toprevent the n⁺ ion doped layer (n⁺ a-Si) that is formed under the lowermolybdenum layer (Mo-b) from being etched. Accordingly, the ratios ofthe pressure and the additional gas are increased.

In Comparative Example 2 (#2), the conventional etching gas, for examplethe chlorine based gas mixed with oxygen gas (O₂), was used. In thatcase, an etching rate (E/R) was about 3509 Å/min and the etchinguniformity was about 6.8%.

In Example 7 (T#7), the etching gas including the chlorine based gasmixed with nitrogen gas (N₂), was used. In that case, the etching rate(E/R) was about 1437 Å/min and the etching uniformity was about 6.7%.

In Example 8 (T#8), the etching gas including the chlorine based gasmixed with argon gas (Ar), was used. In that case, the etching rate(E/R) was about 1684 Å/min and the etching uniformity was about 6.9%.

In Example 9 (T#9), the etching gas including the chlorine based gasmixed with helium gas (He), was used. In that case, the etching rate(E/R) was about 1637 Å/min and the etching uniformity was about 7.1%.

When Comparative Example 2 is compared with Examples 7, 8 and 9, theetching rate (E/R) in Examples 7, 8 and 9 is smaller than that inComparative Example 2, but Examples 7, 8 and 9 may be enough to beapplied to the etching process. The etching uniformity in Examples 7, 8and 9 is substantially same as in Comparative Example 2.

Therefore, as illustrated in Tables 1, 2 and 3, the etching uniformityin etching the upper and lower molybdenum layers (Mo-t, Mo-b) using themixed gas including the chlorine based gas mixed with the additional gashaving one of nitrogen gas (N₂), argon gas (Ar) and helium gas (He), issubstantially same as that in etching the upper and lower molybdenumlayers using conventional oxygen gas (O2).

FIG. 3 is scanning electron microscope (“SEM”) images illustratingetching stringers according to a power density in etching conditions forupper molybdenum.

The SEM pictures illustrated in FIG. 3, show a channel portion and aline portion, after etching the upper molybdenum layer having theMo/Al/Mo layer with the corresponding source power density and biaspower density conditions, and then sequentially etching the aluminumlayer and the lower molybdenum layer.

Comparative Example 3 (#3) shows the channel and line portions, afteretching the upper molybdenum layer with the condition that the sourcepower density was about 0.365 W/cm² and the bias power density was about0.122 W/cm². Comparative Example 4 (#4) shows the channel and lineportions, after etching the upper molybdenum layer with the conditionthe source power density was about 0.73 W/cm² and the bias power densitywas about 0.244 W/cm².

Referring to the SEM pictures of Comparative Example 3 and ComparativeExample 4, a surface of the etched metal pattern includes metalremnants, and the metal remnants having a stringer remain at an edgeportion of the etched metal pattern.

Example 10 (T#10) shows the line portion, after etching the uppermolybdenum layer with the condition that the source power density wasabout 1.095 W/cm² and the bias power density was about 0.366 W/cm².Example 11 (T#11) shows the channel and line portions, after etching theupper molybdenum layer with the condition that the source power densitywas about 1.825 W/cm² and the bias power density was about 0.61 W/cm².

Referring to the SEM pictures of Example 10 and Example 11, the surfaceand the edge portion of the etched metal pattern include little metalremnants. The stringer due to the metal remnants does not occur in thepower densities used in Example 10 and Example 11.

Example Embodiment 2 Method for Manufacturing a Display Substrate

FIG. 4 is a plan view illustrating a display substrate according to anexample embodiment of the present invention. FIGS. 5A to 8 arecross-sectional views illustrating a method for manufacturing a displaysubstrate according to a second example embodiment of the presentinvention.

FIGS. 5A and 5B are cross-sectional views illustrating the method formanufacturing the display substrate using a first mask.

Referring to FIGS. 4, 5A and 5B, a gate metal layer 310 is deposited ona base substrate 101 via a sputtering process. The gate metal layer 310includes a double layer having a low-resistivity metal layer 311 and anupper layer 312. For example, the low-resistivity metal layer 311includes aluminum or aluminum alloy, and the upper layer 312 includesmolybdenum or molybdenum alloy.

A first photoresist layer is formed on the gate metal layer 310, andthen the first photoresist layer is patterned using the first mask, toform a first photoresist pattern PR1. The gate metal layer 310 is etchedusing the first photoresist pattern PR1, to form a gate patternincluding a gate line GLn, a gate electrode GE and a storage common lineSTL.

The gate metal layer 310 may be wet-etched or dry-etched. Preferably, asexplained above in FIGS. 1A to 1C, in etching the gate metal layer 310,an oxygen layer of the upper layer 312, the upper layer 312, the oxygenlayer of the low-resistivity metal layer 311 and the low-resistivitymetal layer 311 are sequentially etched with the first to fourthdry-etching conditions.

FIGS. 6A to 6D are cross-sectional views illustrating the method formanufacturing the display substrate using a second mask.

Referring to FIGS. 4 and 6A, a gate insulating layer 320 and asemiconductor layer 330 including a silicon nitride (SiNx) layer areformed on the base substrate 301 on which the gate pattern is formed,via a plasma enhanced chemical vapor deposition (“PECVD”) process. Thesemiconductor layer 330 includes an active layer 331 having amorphoussilicon (a-Si:H), and an ohmic contact layer 332 doped with n⁺ ion at ahigh concentration.

Then, a source metal layer 340 is deposited on the ohmic contact layer332. The source metal layer 340 has a triple layer including a lowerlayer 341, a low-resistivity metal layer 342 and an upper layer 343sequentially formed. The lower layer 341 includes molybdenum ormolybdenum alloy, the low-resistivity metal layer includes aluminum oraluminum alloy, and the upper layer includes molybdenum or molybdenumalloy.

A second photoresist layer is formed on the base substrate 301 on whichthe source metal layer 340 is formed, and then, a second photoresistpattern (PR2) is formed by using the second mask having a slit.

The second photoresist pattern PR2 includes a first picture pattern PR21and a second picture pattern PR22. The first picture pattern PR21corresponds to an area in which a source electrode SE, a drain electrodeDE, and a source line DLm of a switching element TFT are formed. Thesecond picture pattern PR22 corresponds to an area in which a channelportion CH of the switching element TFT is formed, and the secondpicture pattern PR22 has a thinner thickness than that of the firstpicture pattern PR21.

Referring to FIGS. 4 and 6B, the source metal layer 340 is patterned byusing the second photoresist pattern PR2, so that the source patternhaving an electrode pattern 340 a and the source line DLm is formed. Theelectrode pattern 340 a corresponds to the source and drain electrodesof the switching element TFT.

The source metal layer 340 is wet-etched. In addition, as explainedabove in FIGS. 1A to 1D, the source metal layer 340 that is wet-etchedmay include a better accurate pattern than the source metal layer 340that is etched with the first to fifth dry-etching conditions.

Referring to FIGS. 4, 6C and 6D, after forming the source pattern, thesemiconductor layer 330 is etched using the second photoresist patternand the source pattern as a mask. Accordingly, semiconductor patterns330 a and 330 b that are patterned along the source pattern, are formedunder the source pattern.

The second photoresist pattern PR2 is removed to have a predeterminedthickness using an oxygen (O2) plasma discharge via the ashing process(or etch back process). The electrode pattern 340 a corresponding to thechannel portion CH of the switching element TFT is partially exposed viathe ashing process. A remaining pattern PR23 of the second photoresistpattern PR2 is formed on the area in which the source electrode SE, thedrain electrode DE, and the source line DLm are formed, via the ashingprocess.

The exposed electrode pattern 340 a is dry-etched by using the remainingpattern PR23 as the mask.

The upper layer 343 of the electrode pattern 340 a is etched with thefirst and second dry-etching conditions, as explained above in FIGS. 1Aand 1B. For example, the oxygen layer formed on the upper layer 343 isetched with the first condition that the pressure is about 15 mT, thesource power is about 2000 W, and the etching gas of 100BCl₃ is used.After removing the oxygen layer formed on the upper layer 343, the upperlayer 343 is etched with the second dry-etching condition.

The second dry-etching condition is that the pressure is about 15 mT,the source power density is between about 1 W/cm² and about 2 W/cm², andthe bias power density is between about 0.3 W/cm² and about 0.6 W/cm².The mixed gas including the chlorine based gas is mixed with theadditional gas having one of argon gas (Ar), nitrogen gas (N₂), heliumgas (He) and sulfur hexafluoride gas (SF₆). The ratio of the additionalgas with respect to the chlorine based gas is between about 50% andabout 200%.

After etching the upper layer 343, the low-resistivity metal layer 342of the electrode pattern 340 a, as illustrated in FIG. 1, is etched withthe third and fourth dry-etching conditions. The oxygen layer formed onthe low-resistivity metal layer 342 is etched with the third dry-etchingcondition that the pressure is about 15 mT, the source power is about2000 W and the etching gas of 20Cl₂/100BCl₃ is used.

After removing the oxygen layer formed on the low-resistivity metallayer 342, the low-resistivity metal layer 342 is etched with the fourthdry-etching condition. The fourth dry-etching condition is that thepressure is between about 10 mT and 30 mT, the source power density isbetween about 0.7 W/cm² and about 1.8 W/cm², and the bias power densityis between about 0.7 W/cm² and about 1.8 W/cm². The mixed gas includingthe chlorine based gas mixed with argon gas (Ar) or nitrogen gas (N₂) isused as the etching gas. The ratio of the argon gas (Ar) or nitrogen gas(N₂) with respect to the chlorine based bas is between about 50% andabout 150%.

After etching the low-resistivity metal layer 342, as explained above inFIG. 1D, the lower layer 341 of the electrode pattern 340 a is etchedwith the fifth dry-etching condition.

The electrode pattern 340 a is patterned to be the source electrode SEand the drain electrode DE, via the dry-etching process mentioned above.The ohmic contact layer 332 exposed between the source and drainelectrodes SE and DE is dry-etched by using the source and drainelectrodes SE and DE as the mask. Thus, the channel portion CH throughwhich the active layer 331 is exposed, is formed between the source anddrain electrodes SE and DE, so that the switching element TFT is formed.

After the fifth dry-etching process, the chlorine ion provided from thechlorine based etching gas is reacted with the low-resistivity metallayer 342 including aluminum or aluminum alloy, to remain on an exposedsurface of the low-resistivity metal layer 342. The post-treatmentprocess is performed to remove the remaining chlorine ion. The surfaceof the low-resistivity metal layer 342 is prevented from being corroded,via the post-treatment process. The post-treatment process is performedwith the same condition as the first example embodiment.

FIG. 7 is a cross-sectional view illustrating the method formanufacturing the display substrate using a third mask. FIG. 8 is across-sectional view illustrating the method for manufacturing thedisplay substrate using a fourth mask.

Referring to FIGS. 4, 7 and 8, a protective insulating layer 350 isformed on the base substrate 301 on which the switching element TFT isformed. The protective insulating layer 350 includes the silicon nitridelayer. A contact hole 353 that partially exposes the drain electrode DE,is formed via a photolithography process using the third mask.

The protective insulating layer 350 including the silicon nitride layeris explained in the present example embodiment, but the protectiveinsulating layer 350 may include an organic layer such as an acrylicmaterial. In addition, the protective insulating layer 350 may includethe double layer having the silicon nitride layer and the organic layersequentially formed.

A transparent conductive material (not shown) is deposited on theprotective insulating layer 350 in which the contact hole 353 is formed.Examples of materials that can be used for the transparent conductivematerial may include indium tin oxide or indium zinc oxide. Accordingly,the transparent conductive material is connected to the drain electrodeDE through the contact hole 353. The transparent conductive material ispatterned by using the fourth mask, to form a pixel electrode PE. Thepixel electrode PE is electrically connected to the switching elementTFT through a contact portion CNT.

Example Embodiment 3 Method for Manufacturing a Display Substrate

FIGS. 9 to 12 are cross-sectional views illustrating a method formanufacturing a display substrate according to a third exampleembodiment of the present invention. The same reference numerals will beused to refer to the same or like parts as those described in the secondexample embodiment and any further repetitive explanation concerning theabove elements will be omitted.

FIG. 9 is a cross-sectional view illustrating the method formanufacturing the display substrate using a first mask and a secondmask.

Referring to FIGS. 4 and 9, a gate pattern including a gate line GLn, agate electrode GE and a storage common line STL, is formed on a basesubstrate 301 by using the first mask. The gate pattern includes adouble layer having a low-resistivity metal layer 311 and an upper layer312. The low-resistivity metal layer 311 includes aluminum or aluminumalloy, and the upper layer 312 includes molybdenum or molybdenum alloy.The gate metal layer 310 may be wet-etched or dry-etched. Preferably, asexplained above in FIGS. 1A to 1C, the gate metal layer is sequentiallyetched with the first to fourth dry-etching conditions.

A gate insulating layer 320, an active layer 331 and an ohmic contactlayer 332 are sequentially formed on the base substrate 301 on which thegate pattern is formed. A semiconductor layer 330 of the switchingelement TFT is formed by using a second photoresist pattern PR2 which ispatterned by the second mask.

FIGS. 10A and 10B are cross-sectional views illustrating the method formanufacturing the display substrate using a third mask.

Referring to FIGS. 4, 10A and 10B, a source metal layer 340 is formed onthe base substrate 301 on which the semiconductor layer 330 of theswitching element TFT is formed. The source metal layer 340 including atriple layer having a lower layer 341, a low-resistivity metal layer 342and an upper layer 342 is sequentially formed. The lower layer 341includes molybdenum or molybdenum alloy, the low-resistivity metal layer342 includes aluminum or aluminum alloy, and the upper layer 342includes molybdenum or molybdenum alloy.

The source metal layer 340 is etched by using a third photoresistpattern PR3 that is patterned by the third mask, to form a sourcepattern including a source electrode SE, a drain electrode DE and asource line DLm. The source metal layer 340, as explained above in FIGS.1A to 1D, is etched with the first to fifth dry-etching conditions, toform the source pattern.

A channel portion CH is formed by using the source and drain electrodesSE and DE as a mask. The base substrate 301 on which the channel portionCH is formed is treated via the post-treatment process, to prevent thelow-resistivity metal layer 342 of the source pattern from beingcorroded.

FIGS. 11 and 12 are cross-sectional views illustrating the method formanufacturing the display substrate using a fourth mask and a fifthmask.

Referring to FIGS. 4, 11 and 12, a protective insulating layer 350 isformed on the base substrate 301 on which the channel portion CH isformed, and a contact hole 353 is formed using the fourth mask. Atransparent conductive material is deposited to make contact with thedrain electrode DE through the contact hole 353. Then, the transparentconductive material is patterned using the fifth mask, to form a pixelelectrode PE.

According to the present invention, the mixed gas including the chlorinebased gas (for example, C₁₂ or HCl) mixed with the additional gas havingone of nitrogen gas (N₂), argon gas (Ar), helium gas (He) and sulfurhexafluoride gas (SF₆), is used for dry-etching of the upper layerincluding molybdenum formed on the aluminum layer, so that the stringerremaining on the metal layer due to the etching gas including oxygen gasmay be removed.

In addition, with the etching condition is that the mixed gas includingnitrogen gas (N₂), argon gas (Ar) or helium gas (He) is used, the sourcepower density is between about 1 W/cm² and about 2 W/cm², and the biaspower density is between about 0.3 W/cm² and about 0.6 W/cm², thestringer remaining on the metal layer may be remarkably enhanced.Accordingly, the line stringer of the low-resistivity line includingaluminum is removed, so that the metal line may be more accurate.

Having described the example embodiments of the present invention andits advantage, it is noted that various changes, substitutions, andalterations can be made herein without departing from the spirit andscope of the invention as defined by appended claims.

1. A method for forming a metal line, the method comprising:sequentially depositing a low-resistivity metal layer having aluminum ona base substrate, and an upper layer having molybdenum on thelow-resistivity metal layer; forming a photoresist pattern having alinear shape on the upper layer; etching the upper layer via a mixed gasusing the photoresist pattern as a mask, the mixed gas including achlorine based gas mixed with an additional gas having at least oneselected from the group consisting of nitrogen gas, argon gas, heliumgas and sulfur hexafluoride gas; and etching the low-resistivity metallayer using the photoresist pattern as the mask.
 2. The method of claim1, wherein a ratio of the additional gas with respect to the chlorinebased gas is between about 50% and about 200%.
 3. The method of claim 2,wherein the upper layer is etched with conditions that a source powerdensity [W/cm²] is between about 1 and about 2, and a bias power density[W/cm²] is between about 0.3 and about 0.6.
 4. The method of claim 1,wherein the low-resistivity metal layer is etched by the mixed gasincluding the chlorine based gas mixed with the argon gas or thenitrogen gas.
 5. The method of claim 4, wherein a ratio of the argon ornitrogen gas with respect to the chlorine based gas is between about 50%and about 150%.
 6. The method of claim 5, wherein the low-resistivitymetal layer is etched with conditions that a source power density[W/cm²] is between about 0.7 and about 1.8, and a bias power density[W/cm²] is between about 0.7 and about 1.8.
 7. The method of claim 1,further comprising removing a corrosive element remaining on the basesubstrate after etching the low-resistivity metal layer.
 8. The methodof claim 7, further comprising forming a lower layer including themolybdenum under the low-resistivity metal layer.
 9. The method of claim8, further comprising etching the lower layer using the mixed gasincluding the chlorine based gas mixed with the additional gas having atleast one selected from the group consisting of nitrogen gas, argon gas,helium gas and sulfur hexafluoride gas, before removing the corrosiveelement.
 10. The method of claim 7, wherein the corrosive element isremoved by using at least one selected from the group consisting of H₂0gas and H₂ gas.
 11. The method of claim 7, wherein the corrosive elementis removed by using a fluorine (F) based gas.
 12. The method formanufacturing a display substrate, the method comprising: forming a gateinsulating layer on a base substrate, a gate pattern having a gate lineand a gate electrode formed on the base substrate; sequentially forminga source metal layer including a lower layer, a low-resistivity layerand an upper layer, the lower layer having molybdenum formed on the gateinsulating layer, the low-resistivity metal layer having aluminum formedon the lower layer, the upper layer having molybdenum formed on thelow-resistivity metal layer; forming a source pattern having a sourceline, a source electrode and a drain electrode by etching the upperlayer using a chlorine based gas mixed with an additional gas having atleast one selected from the group consisting of nitrogen gas, argon gas,helium gas and sulfur hexafluoride gas; forming a protective insulatinglayer having a contact hole formed in the protective insulating layer,the contact hole partially exposing the drain electrode; and forming apixel electrode electrically connected to the drain electrode throughthe contact hole.
 13. The method of claim 12, wherein a ratio of theadditional gas with respect to the chlorine based gas is between about50% and about 200%.
 14. The method of clam 13, wherein the upper layeris etched with conditions that a source power density [W/cm²] is betweenabout 1 and about 2, and a bias power density [W/cm²] is between about0.3 and about 0.6.
 15. The method of claim 14, wherein forming thesource pattern comprises: forming an electrode pattern and the sourceline, via etching the source metal layer; etching an upper layer of theelectrode pattern using the chlorine based gas mixed with the additionalgas having at least one selected from the group consisting of nitrogengas, argon gas, helium gas and sulfur hexafluoride gas; etching alow-resistivity metal layer of the electrode pattern using the mixed gasincluding the chlorine based gas mixed with argon gas or nitrogen gas;and etching a lower layer of the electrode pattern using the chlorinebased gas mixed with the additional gas having at least one selectedfrom the group consisting of nitrogen gas, argon gas, helium gas, andsulfur hexafluoride gas.
 16. The method of claim 15, wherein thelow-resistivity metal layer is etched with conditions that a chamberpressure is between about 10 and about 30, the source power density[W/cm²] is between about 0.7 and about 1.8, and the bias power density[W/cm²] is between about 0.7 and about 1.8.
 17. The method of claim 14,wherein forming the source pattern comprises: etching an upper layer ofthe source metal layer using chlorine based gas mixed with theadditional gas having at least one selected from the group consisting ofnitrogen gas, argon gas, helium gas and sulfur hexafluoride gas; etchinga low-resistivity metal layer of the source metal layer using thechlorine based gas mixed with argon gas or nitrogen gas; and forming thesource line, the source electrode and the drain electrode by etching alower layer of the source metal layer using the chlorine based gas mixedwith the additional gas having at least one selected from the groupconsisting of nitrogen gas, argon gas, helium gas and sulfurhexafluoride gas.
 18. The method of claim 12, further comprisingremoving a corrosive element corroding the low-resistivity metal layer,after forming the source pattern.
 19. The method of claim 18, whereinthe corrosive element is removed by using at least one selected from thegroup consisting of H₂0 gas and H₂ gas.
 20. The method of claim 18,wherein the corrosive element is removed by using a fluorine (F) basedgas.